This is an improvement in fluid-operated clutch and/or brake devices of the type described in U.S. Pat. No. 3,378,121. That patent discloses vacuum-operated clutch and brake devices with magnetic valves having extremely fast actuation time with extremely fast switching time in both clutch and brake constructions. Clutch and brake devices in accordance with that patent have many advantages over prior art clutch brakes. Such vacuum-operated clutch and brake devices while having outstanding value, do have certain limitations. It is known that as the thin flat disks used for clutching or braking are increased in diameters, problems such as disk buckling during manufacturing, cracking at the disk hub during torque transmission and partial disk collapsing can occur. These problems can occur since increasing the diameter of the disk by a factor of 2 results in increasing the acting pneumatic force on the disk by a factor of 4 and the torque by a factor of 8. The disk inertia increases as the 4th power of the diameter. As a result, the flat disk described in U.S. Pat. No. 3,378,121 is best for small disks, generally not exceeding 8" diameter.
The leakage gap between the coupling disk and friction pad of the prior art as shown in said U.S. Pat. No. 3,378,121 can vary with distortion of the disk as well as by wearing away of friction material with repeated usage. It is desirable to increase the advantageous properties of the prior art by providing constructions which avoid wear-related variation in response, are formed by simplified methods, and which enable disks to be used which have maximum strength and flexibility for increased speed of operation, higher energy efficiency and long life.